In case of analysis appliances of the kind in question a liquid sample to be analyzed is generally automatically sucked in by means of a sample dispenser from a vessel containing the sample to be analyzed by means of a cannula and, after appropriate new positioning of the sample dispenser, is injected into the analysis chamber, which is for example a reactor in which the sample is evaporated, and subsequently analyzed.
For various reasons it is desirable that the analysis chamber before, during, and after analysis is exposed only to a limited extent to ambient air. For example, it may be desirable that before the analysis ambient air cannot penetrate into the analysis chamber and possibly falsify the measurement. When the sample to be analyzed is evaporated in the analysis chamber, the gases that are produced thereby should be supplied as completely as possible to appropriate sensors and should not escape in an uncontrolled fashion into the environment. After the analysis, the analysis chamber can be flushed, for example, with an inert gas that also should not escape in an uncontrolled fashion into the environment. On the other hand, the cannula of the sample dispenser must be insertable into the analysis chamber so that an access to the analysis chamber is required for the cannula.
Up to now the aforementioned access to the analysis chamber is realized by means of a septum that is simply punctured by means of the cannula of the sample dispenser and that, at least when new, provides a sufficient sealing action for the analysis chamber with inserted cannula as well as after pulling out the cannula. Since however automatic sample dispensers in general operate very precisely, the punctuation of the septum occurs always at the same location which leads to a fast aging of the septum that therefore must be exchanged relatively frequently. In case of automatic analysis appliances that operate sequentially without supervision for many hours and theoretically can analyze thousands of samples without requiring a human intervention for maintenance, the exchange of the septum that up to now could only be done manually is a significant impairment of the efficiency and represents a significant cost factor.